AGM batteries (like the Motobatt) are great – light weight, high cranking Amps, low internal resistance, vibration resistance, don’t sulphate and hold a charge for long periods. There are a lot of advantages, but they do unfortunately (as with everything in life) have some disadvantages.

The main one being that they are very sensitive to overcharging. AGM batteries can be charged at 2.40V/cell (14.4V) without problem in short bursts; however, the float/maintenance charge should be 2.25/cell (13.5V) and warm ambient temperatures require even lower voltages. Most motorcycle charging systems are designed for flooded lead acid batteries (like the XT) and have a fixed float voltage of 14.40V (2.40V/cell) at engine speeds above 3000rpm; a direct replacement with an AGM battery could give trouble by exposing the battery to overcharging on a long ride, particularly in hot weather. Almost all automotive charging systems produce 13.6-14.4V, which is too much for a fully-charged AGM battery over a sustained period.

AGM batteries do not like heat and should be installed away from sources of high temperature. It is recommended to stop charging altogether if the battery core reaches 49C+.

You need to check that your battery charger/conditioner can deal with AGM batteries. Chargers designed for AGM batteries should have a temperature sensor (to self-regulate charging voltage to match ambient temperature) and special charging stages, the last being a "float" voltage setting must be 12.7-13.6V to prevent permanent damage.

Interestingly the ABS Ten has an OE AGM battery which has its own built in temperature dependent secondary charge regulator. It also says in the handbook “take to your nearest dealer for recharging” – as if anyone’s going to do that!

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